Optical deflector

Abstract

An optical deflector is provided which can effectively suppress occurrence of a ringing phenomenon when a piezoelectric actuator is driven with a voltage signal of a sawtooth waveform. An optical deflector A 1 includes a control circuit 20 that detects a mechanical natural frequency relevant to swinging about a second axis X 2 of a movable part 9 . The control circuit 20 applies a voltage signal of a sawtooth waveform from which the natural frequency and a harmonic component thereof are removed to outside piezoelectric actuators 10 a and 10 b . The control circuit 20 removes a frequency component, which is equal to or greater than a second threshold value G 2 within a predetermined frequency range out of frequency components of a voltage signal output from a detecting piezoelectric body 62 , from a drive voltage.

What is claimed is: 
     
       1. An optical deflector comprising:
 a mirror part configured to have a reflective plane; 
 a support part configured to support the mirror part; 
 a piezoelectric actuator of which one end is connected to the mirror part, of which the other end is connected to the support part, and which swings the mirror part about a predetermined axis relative to the support part by piezoelectric driving; 
 a detecting piezoelectric element which outputs a detection voltage based on bending deformation due to vibration transmitted by the piezoelectric actuator, and 
 a control unit configured to control a drive voltage to be applied to the piezoelectric actuator, 
 wherein the control unit includes a natural frequency detecting unit configured to detect a mechanical natural frequency relevant to the swinging of the mirror part about the predetermined axis, a voltage signal generating unit configured to generate a voltage signal of a sawtooth waveform periodically repeating an increase and a decrease of a voltage value with a constant amplitude, and a removal unit configured to remove a predetermined frequency component, and 
 wherein a voltage signal obtained by removing the natural frequency detected by the natural frequency detecting unit and a harmonic component of the natural frequency from the voltage signal generated by the voltage signal generating unit within a predetermined frequency range is applied as the drive voltage to the piezoelectric actuator and thereafter a frequency component which is equal to or greater than a predetermined value within the predetermined frequency range, out of the frequency components of the detection voltage output from the detecting piezoelectric element, is removed from the drive voltage. 
 
     
     
       2. The optical deflector according to  claim 1 , wherein the natural frequency detecting unit includes a sinusoidal wave generating unit configured to generate a voltage signal of a sinusoidal waveform,
 wherein the sinusoidal wave generating unit generates a voltage signal of a sinusoidal waveform for each frequency in the range of a predetermined first frequency to a second frequency, and 
 wherein the natural frequency detecting unit detects the frequency of the sinusoidal waveform, which is equal to or greater than a predetermined value out of the frequency components of the detection voltage output from the detecting piezoelectric element when the voltage signals of the sinusoidal waveform generated by the sinusoidal wave generating unit are applied to the piezoelectric actuator, as the natural frequency. 
 
     
     
       3. The optical deflector according to  claim 1 , wherein the piezoelectric actuator includes a plurality of piezoelectric cantilevers configured to be bending-deformed by piezoelectric driving, the plurality of piezoelectric cantilevers are arranged side by side so as to neighbor both ends of each piezoelectric cantilever, the ends are mechanically connected to fold back to the neighboring piezoelectric cantilever so as to accumulate the bending deformation, and the respective piezoelectric cantilevers are formed to be bending-deformed in a direction perpendicular to the arranging direction of the piezoelectric cantilevers.